1. Field of the Invention
The present invention relates to novel organic gold compounds and, more precisely, to those used for forming a metal gold by pyrolysis.
Specifically, the organic gold compounds of the present invention have such an improved property that show a high solubility in terpene alcohol solvents such as terpineol and in other solvents with an excellent stability of the resulting solution for a long period of time. A paste composition containing the compound in a form of solution may be used for forming a thin metal gold layer or film on a substrate.
2. Prior Art Description
Various organic gold compounds are known.
For instance, JP-B-37-2955 discloses gold tertiary alkylmercaptides; JP-B-40-22468 discloses gold secondary alkylmercaptides; and JP-B-41-18357 discloses gold arylmercaptides. (The term "JP-B" as used herein means an "examined Japanese patent publication.)
The above-mentioned conventional compounds are all represented by a formula (2): EQU Au--SR (2)
where Au represents a monovalent gold atom; and R represents a hydrocarbon group.
The known compounds are obtained by reacting a halogenoauric acid and a mercaptan in a proportion of 3 mols or more of mercaptan to mol of halogenoauric acid; or by reacting a compound of a formula (3): EQU R.sub.2 S.AuX (3)
where Au represents a monovalent gold atom, X represents a halogen atom, R represents a hydrocarbon group, and AuX is bonded to the sulfur atom by coordination bond, and a mercaptan in a proportion of one mol or more of mercaptan to mol of compound of formula (3).
The above-mentioned known compounds have a low solubility in low-polar organic solvents, such as terpineol, which are usually used as a vehicle of ink for screen-printing. In fact, they are substantially insoluble in such low-polar organic solvents at room temperature and they may only slightly be dissolved therein only under heat.
Therefore, it is impossible to obtain a paste of such compounds in high concentration, and the gold content in a paste containing the compound is limited in a low level and the thickness of the gold film to be formed therefrom is also limited. Additionally, selection of additives to be used for elevating the printability and adhesiveness between the gold film and the substrate as well as the amount of such additives is extremely limited.